Tuesday, August 10, 2004

Using X headers with Exchange

X-headers are user defined fields that can (and are) inserted into a mail header that can serve a number of roles and purposes. Some common ones that are used are x-mailer which descibes the name of the software used to send that email and x-scl which is used to store the IMF SCL value when a message is archived to the ucearchive directory by the IMF (note this is not used to pass the SCL between servers this is done though the xexch50 blob during message transfer).

If you want to make use of a x-header in a Exchange sink or CDO script its pretty easy. First off all you need to know is what the name of the x-header is. If your not sure i find the best way to find out is to look at a serial version of the email. For this you can save the message to a eml file using a script like this and then open the eml file in notepad.

set msgobj = createobject("CDO.Message")
msgobj.datasource.open mailurl
set stm = msgobj.getstream()
stm.savetofile "d:\myemail.eml"

Once you know what the X header field name is to retrieve or set a X header in a sink or script all you need to do is append the name of the x header to urn:schemas:mailheader: . For example one way of telling if a email is a delivery report of some sort is to see if X-DSNContext is set in the header of a message for example

set msgobj = createobject("CDO.Message")
msgobj.datasource.open mailurl

if msgobj.fields("urn:schemas:mailheader:X-DSNContext") <> "" then
Wscript.echo "Delivery Report"
else
Wscript.echo "Normal"
end if

If you want to create your own X-header in a SMTP event sink (say you wanted this to be processed by another sink somewhere else). It would look like this

Sub ISMTPOnArrival_OnArrival(ByVal Msg, EventStatus )

on error resume next
msg.fields("urn:schemas:mailheader:X-myfield") = "Email-Okay"
msg.fields.update
msg.datasource.save

End Sub